Use of oxides of manganese in electro-depositable compositions

ABSTRACT

THIS INVENTION RELATES TO NOVEL, PIGMENTED, ELECTRODEPOSITABLE COMPOSITIONS. MORE PARTICULARLY, THIS INVENTION RELATES TO THE USE OF OXIDES OF MANGANESE TO PRODUCE BLACK OR DARK-COLORED ELECTRODEPOSITABLE COMPOSITIONS, AND WHICH IN SOME CASES ALSO PRODUCE A DRYING EFFECT IN THE DEPOSITED FILM. SAID FILMS DO NOT EXHIBIT THE PIGSKINNING EFFECT OBSERVED WHEN CARBON BLACK PIGMENTS ARE USED.

United States Pa ent fine 3,594,339 Patented July 20, 1971 US. Cl.260-18 13 Claims ABSTRACT OF THE DISCLOSURE This invention relates tonovel, pigmented electrodepositable compositions. More particularly,this invention relates to the use of oxides of manganese to produceblack or dark-colored electrodepositable compositions, and which in somecases also produce a drying effect in the deposited film. Said films donot exhibit the pigskinning effect observed when carbon black pigmentsare used.

CROSS-REFERENCES TO RELATED APPLICATIONS This application is acontinuation-in-part application of US. Ser. No. 791,129, filed Jan. 14,1969, which is a divisional application of US. Ser. No. 591,708, filedNov. 3, 1966 now abandoned.

This invention relates to novel, pigmented electrodepositablecompositions. More particularly, this invention relates to the use ofoxides of manganese to produce black or dark-colored electrodepositablecompositions, and which in some cases also produce a drying effect inthe deposited film.

Recently, electrodeposition has been achieving wide industrialacceptance as a method of applying protective coatings. The coatingsachieved have excellent properties for many applications andelectrodeposition results in a coating which does not run or wash offduring baking. Virtually any conductive substrate may be coated byelectrodeposition. The most commonly employed substrates include thebase metals such as iron, steel, aluminum, copper, zinc, brass, tin,nickel and chromium, as well a other metals and pretreated metals;impregnated paper or other substrates rendered conductive under the conditions employed may also be coated.

Electrodeposition of certain materials, including waxes, natural andsynthetic resins, have been known in the art for some time. Likewise, arecent US. Pat. No. 3,230,162, describes a method and compositionspresently utilized in the field of automotive finishing and industrialcoatings.

While electrodeposition is in many respects advantageous compared toordinary application methods, problems have arisen in the fact thatcarbon black, universallyused black pigment, displays severalundesirable characteristics in electrodeposition composition. Whilecarbon black pigments successfully deposit in electrodepositioncompositions at low voltages, at higher voltages (for example, aboveabout 200 volts), a problem of pig-skinning is encountered. Pig-skinningmay be defined as a. rough uneven surface as compared to the normaldesirable smooth surface obtained in a conventional paint formulation.

It has now been found that the use of oxides of manganese as a pigmentsubstitute for carbon black produces black or dark brown films which maybe coated at higher voltages to produce smooth films. Pig-skinning seemsto be an inherent characteristic of carbon black which is notencountered with the oxides of manganese. The vehicle resin plays littlepart in producing this effect, and improvement is seen in substitutingmanganese for carbon black in virtually every electrodepositablecomposition.

Likewise, it has been found that the oxides of manganese promote thedrying of coating films containing siccative oils vehicles, i.e., filmscomprising vehicles which contain drying oils or semi-drying oils.

The oxides of manganese broadly may be employed in the compositions ofthe invention. Examples of such oxides include mangano-manganic oxide,Mn O manganese sesquioxide Mn O and manganese dioxide, MnO

Since the oxides of manganese exist in nature, as well as beingobtainable in a relatively chemically pure state, and since thesematerials are chiefly oxides of manganese and display a black or darkbrown color, it is within the scope of the invention to utilize thesenaturallyoccurring mineral oxides in the compositions of the invention.The chief oxide minerals of manganese include pyrolusite, psilomelane,manganite and hausmannate.

In the electrodeposition process, the articles to be electrocoated areimmersed in an aqueous dispersion of a solubilized, ionized,film-forming material such as a synthetic organic vehicle resin. Anelectric current is passed between the article to be coated serving asan electrode and a counter-electrode to cause deposition of a coating ofthe vehicle resin on the articles. The articles are then withdrawn fromthe bath, usually rinsed and then the coating either air-dried or bakedin the manner of a conventional finish.

A number of electrodepositable resins are known and can be employed toprovide the electrodepositable com positions which may be treated by theprocess of this invention. Virtually any water-soluble,water-dispersible or water-emulsifiable polyacid or polybasic resinousmaterial can be electrodeposited and, if fihn-forming, provides coatingswhich may be suitable for certain purposes. Any such electrodepositablecomposition is included among those which can be employed in the presentinvention, even though the coating obtained might not be entirelysatisfactory for certain specialized uses.

Presently, the most widely used electrodeposition vehicle resins aresynthetic polycarboxylic acid resinous materials which include areaction product or adduct of the drying oil or semi-drying oil fattyacid ester with a dicarboxylic acid or anhydride. By drying oil orsemidrying oil fatty acid esters are meant esters of fatty acids whichare or can be derived from drying oils or semidrying oils, or from suchsources as tall oil. Such fatty acids are characterized by containing atleast a portion of polyunsaturated fatty acids. Preferably, the dryingoil or semi-drying oil per se is employed. Generally, drying oils arethose oils which have an iodine value of above about 130, and thesemi-drying oils are those which have an iodine value of about to 130,as determined by method ASTM-D1467-57T. Examples of such esters includelinseed oil, soya oil, safilower oil,

perilla oil, tung oil, oiticica oil, poppyseed oil, sunflower oil, talloil esters, walnut oil, dehydrated castor oil, herring oil, menhadenoil, sardine oil, and the like.

Also included among such esters are those in which the esters themselvesare modified with other acids, including saturated, unsaturated oraromatic acids such as butyric acid, stearic acid, linoleic acid,phthalic acid, isophthalic acid, terephthalic acid or benzoic acid, oran anhydride of such an acid. One inexpensive acid material which hasbeen found to produce good results in many instances is rosin, which iscomposed of chiefly abietic acid and other resin acids. Theacid-modified esters are made by transesterification of the ester, as byforming a dior monoglyceride by alcoholysis, followed by esterificationwith the acid. They may also be obtained by reacting oil acids with apolyol and reacting the acid with the partial ester. In addition toglycerol, alcoholysis can be carried out using other polyols such astrimethylolpropane, pentaerythritol, sorbitol and the like. If desired,the esters can also be modified with monomers such as cyclopentadiene orstyrene and the modified esters produced thereby can be utilized herein.Similarly, other esters of unsaturated fatty acids, for example, thoseprepared by the esterification of tall oil fatty acids with polyols, arealso useful.

Also included within the terms drying oil fatty acid esters as set forthherein are alkyd resins prepared utilizing semi-drying or drying oils;esters of epoxides with such fatty acids, including esters of diglycidylethers of polyhydric compounds as well as other mono-, diandpolyepoxides, semi-drying oi-l fatty acid esters of polyols, such asbutanediol, trimethylolethane, trimethylolpropane, trimethylolhexane,pentaerythritol, and the like; and semidrying or drying fatty acidesters of resinous polyols such as homopolymers or copolymers ofunsaturated aliphatic alcohols, e.g., allyl alcohol or methallyl alcoholincluding copolymers of such alcohols with styrene or otherethylenically unsaturated monomers or with non-oil modified alkyd resinscontaining free hydroxyl groups.

Any alpha, beta-ethylenically unsaturated dicarboxylic acid or anhydridecan be employed to produce the reaction products described herein. Theseinclude such anhydrides as maleic anhydride, itaconic anhydride, andother similar anhydrides. Instead of the anhydride, there may also beused ethylenically unsaturated dicarboxylic acids which form anhydrides,for example, maleic acid or itaconic acid. These acids appear tofunction by first forming the anhydride. Fumaric acid, which does notform an anhydride, may also be utilized, although in many instances itrequires more stringent conditions than the uu saturated dicarboxylicacid anhydrides or acids which form such anhydrides. Mixtures of any ofthe above acids or anhydrides may also be utilized. Generally speaking,the anhydride or acid employed contains from 4 to 12 carbon atoms,although longer chain compounds can be used if so desired.

While the exact nature of the reaction product of the acid or anhydridewith the fatty acid ester is not known with certainty, it is believedthat the reaction takes place by addition of the unsaturated linkage ofthe acid or anhydride to the carbon chain of the oil. In the case ofnonconjugated double bonds, such as are present in linseed oil, thereaction may take place with the methylene group adjacent thenon-conjugated double bond. In the case of oils having conjugated doublebonds, such as tung oil, the reaction is probably of the Diels-Aldertype.

The reaction between the acid or acid anhydride and the drying oil orsemi-drying oil fatty acid ester takes place readily Without the use ofa catalyst and at temperatures in the range of about 100 C. to about 300C. or higher, with the reaction generally being carried out betweenabout 200 C. and about 250 C.

While the reaction products can be comprised solely of adducts of thefatty acid ester and the dicarboxylic acid or anhydride, in manyinstances it is desirable to incorporate into the reaction productanother ethylenically unsaturated monomer. The use of such monomer oftenproduces films and coatings which are harder and more resistant toabrasion and which may have other similar desirable characteristics. Forthis purpose, any ethylenically unsaturated monomer can be employed.Examples of such monomers include monoolefinie and diolefinichydrocarbons such as styrene, alpha-methyl styrene, alpha-butyl styrene,vinyl toluene, butadiene-l,3-isoprene and the like; halogenatedmonoolefinic and diolefinic hydrocarbons, such as alpha-chlorostyrene,alpha-bromostyrene, chlorobutadiene and similar compounds; esters oforganic and inorganic acids, such as vinyl acetate, vinyl propionate,vinyl 2-chlorobenzoate, methyl acrylate, ethyl methacrylate, butylmethacrylate, heptyl acrylate, deeyl methacrylate, methyl crotonate,isopropenyl acetate, vinyl alphabromopropionate, vinylalpha-chlorovalerate, allyl chloride, allyl cyanide, allyl bromide,allyl acetate, dimethyl itaconate, dibutyl itaconate, ethylalpha-chloroacrylate, isopropyl alpha-bromoacrylate, deeylalpha-chloroacrylatc, dimethyl maleate, diethyl maleate, dimethylfumarate, diethyl fumarate, and diethyl glutaconate; organic nitriles,such as acrylonitrile, methacrylonitrile, ethacrylonitrile, and thelike.

As is apparent from the above discussion and the examples set forth,which, of course, do not include all of the ethylenically unsaturatedmonomers which may be employed, any such monomer can be utilized. Thepreferred class of monomers can be described by the formula: 4

R1CC=R5 it. where R and R are hydrogen or alkyl, R, is hydrogen, alkylor carboxyalkyl and R is cyano, aryl, alkyl, alkenyl, aralkyl, alkaryl,alkoxycarbonyl or aryloxycarbonyl. The preferred compounds are styrene,substituted styrenes, alkyl acrylates, alkyl rnethacrylates, diolefins,and acrylonitrile.

The reaction of the fatty acid ester, the acid or anhydride or anyadditional monomer or monomers can be carried out concurrently, that is,with each of the components of the reaction product being mixed togetherand heated to reaction temperature. However, because the monomer and theacid or anhydride are often quite reactive with each other, the oil orother fatty acid ester is preferably first reacted with the acid or acidanhydride, and then this product is subsequently reacted with anyethylenically unsaturated monomer or monomers employed. For example, areaction product of linseed oil, maleic anhydride and styrene is made byfirst reacting maleic anhydride with linseed oil and then reacting themaleinized oil with styrene. When the process is carried out in thismanner, the reaction of the additional monomer with the initial reactionproduct is usually carried out at somewhat lower temperautres, usuallybetween about 25 C. and 200 C.

The proportions of each of the components going to make up the reactionproduct are ordinarily not critical. Generally speaking, between about10 percent and about 45 percent by weight of the unsaturated acid oracid anhydride is reacted with from about 55 percent to about 90 percentby weight of fatty acid ester. In the presently preferred products,usually 15 percent to 30 percent of anhydride and 70 percent to percentof oil ester are employed. If an ethylenically unsaturated monomer isincorporated in the reaction product, it is typically used in amountsbetween about -5 percent and about 35 percent by weight, based upon thetotal weight of acid or anhydride and ester, with between 10 percent and25 percent being used in those products preferred at present. Thus, inmost instances the total composition of the reaction product maycomprise from about 35 percent to about percent by weight of the fattyacid ester and from about 10 percent to about 65 percent of the acid oranhydride and other monomer combined with between about 6 percent andabout 45 percent of the acid or anhydride always present.

The products produced in the above manner are comprised of polymericchains of moderate length. The average molecular weight of the productsto be used in electro-deposition should be low enough so that its flowcharacteristics at high solids are maintained, but high enough toprovide adequate throwing power. The desirable molecular weight levelsvary with the coating composition and conditions employed. Generallythose products having molecular weights of up to 10,000 or somewhathigher have given the best results.

Neutralization of these products is accomplished by reaction of all orpart of the dicarboxylic anhydride groups with a base, usually an amine.Usually up to about half of such groups are neutralized in unesterifiedadducts; the partially esterified products are often neutralized to agreater extent, based on unesterified acid groups remaining.

It is preferred in certain instances that the neutralization reaction becarried out in such a manner that amido groups are attached to part ofthe carbonyl carbon atoms derived from the dicarboxylic acid oranhydride. By amido groups are meant trivalent nitrogen atoms attachedWith one valence to the carbonyl carbon atom with the other two valencesbeing linked to hydrogen or carbon atoms in the same or differentorganic radicals. Arnido groups are formed, for example, when thereaction with the neutralizing base is carried out with a water solutionof ammonia, a primary amine or a secondary amine, or when the product isreacted with such an amine in the absence of water.

Compositions within this general class are described in US. Pats. Nos.3,366,563 and 3,369,983.

Another vehicle comprises the fatty acid ester, unsaturated acid oranhydride reaction products and any additional unsaturated modifyingmaterials (as described above) which are further reacted with thepolyol.

Essentially any polyol can be employed, but diols are preferred. Whenhigher polyols, such as trimethylol propane glycerol, pentaerythritoland the like are utilized, they are employed in small amounts, or inconjunction with the diol, or in the presence of a monohydric alcohol,and are used with adducts having a relatively low proportion of acidiccomponent. The various diols that can be employed include, for example,ethylene glycol; 1,2- propylene glycol; 1,4-butanediol; 1,5-pentanediol;Z-methyl-Z-n-propyl-1,3-propanediol, and similar higher or substitutedalkylene glycols, containing up to about 20 carbon atoms or more. Glycolethers may also be employed, such as diethylene glycol, triethyleneglycol, poly(oxytetrarnethylene)glycols and the like, those havingmolecular Weights of up to about 400 being most useful. Waterinsolublediols are often preferable, and especially desirable water-dispersedcompositions for electrodeposition are obtained using2,2-bis(4-hydroxycyclohexyl)propane (which has given the best results),neopentyl glycol, 1,l-isopropylidene-bis (p-phenyleneoxy)di 2 propanol,and similar diols.

The proportions of polyol and ester-anhydride adduct that are employeddepend upon various factors, but are, in general, limited only by theneed to avoid gelation of the product. The total functionality of thereactants is a guide to determining the optimum proportions to beemployed, and in most instances should not be greater than about 2. Bytotal functionality is meant the total number of anhydride and hydroxylgroups divided by the total number of molecules of polyol and adduct.The numbers involved are, of course, average figures, and obviously manyfactors are taken into consideration in determining functionality, thesebeing well-known in the art. When monomeric constituents are used, theirfunctionality is relatively easily determined; but with resinousproducts such as the adducts herein not only the proportion of anhydridein the adduct but also the bodying effect due to heating and similarconsiderations should be taken into account. In any event, one caneasily determine whether any particular combination of reactants resultsin a gelled product, and as mentioned above, gelation can often bereversed by adding a monohydric alcohol.

In most instances, the reaction products herein are made from about 65percent to about 98 percent of ester-anhydride adduct and about 2percent to about 35 percent of a diol, these percentages being byweight. However, it Will be understood that depending upon the molecularweights of the reactants, varying amounts within these ranges or outsidethese ranges are employed with particular reaction systems.

In many instances, only part of the anhydride groups of the adduct,e.g., about 10 percent, are reacted with the polyol. Of those anhydridegroups reacted, it is preferred that only one of the carboxyl groups isesterified in each instance. This is relatively easily accomplishedbecause the half-ester of the dicarboxylic acid anhydride moietiespresent is preferentially obtained before the full ester begins to beformed. In addition, production of the full ester generally requiresmore stringent conditions, such as higher temperatures, even when anexcess of hydroxyl groups are present. Thus, while it is not necessarythat each anhydride form the half-ester and some of the dicarboxylicgroups may be fully esterified, in actual practice the half-esters ofthe dicarboxylic acid moieties are usually obtained.

The reaction with the polyol is ordinarily carried out by admixing theinitial reaction product of the fatty ester, the acid or anhydride, andany additional monomer with the polyol. The reaction at room temperatureis quite slow, and thus it is preferred to heat the reaction mixturemoderately, i.e., to about C. or higher. The preferred maximumtemperature is that at which the full ester begins to be formed, whichvaries With the particular polyol and which is in most cases about 180C., but higher temperatures up to about 300 C., can be used if desired,for example, when the number of hydroxyl groups present does not exceedthe number of anhydride groups present.

When the reaction is carried out as described, the product contains asubstantial part of the original acidity derived from the dicarboxylicacid or anhydride; ordinarily the product should have an acid number ofat least about 20. To provide a Water-dispersed product, such as is usedin electrodeposition processes, at least part of the remaining acidicgroups are neutralized by reaction of the partiallyesterified productwith a base.

The polyol reaction products are more fully described in applicationSer. No. 450,205, filed Apr. 22, 1965.

Another type of electrodepositable coating composition which givesdesirable results are the water-dispersible coating compositionscomprising at least partially neu tralized interpolymers of hydroxyalkylesters of unsaturated carboxylic acids, unsaturated carboxylic acids andat least one other ethylenically unsaturated monomer. These are employedin the composition along with an amine-aldehyde condensation product,with the interpolymer usually making from about 50 percent to aboutpercent by weight of the resinous composition.

The acid monomer of the interpolymer is usually acrylic acid ormethacrylic acid, but other ethylenically unsaturated monocarboxylic anddicarboxylic acids, such as ethacrylic acid, crotonic acid, maleic acid,or other acids of up to about 6 carbon atoms can also be employed. Thehydroxyalkyl ester is usually hydroxyethyl or hydroxypropyl acrylate ormethacrylate, but also desirable are the various hydroxyalkyl esters ofthe above acids having, for example, up to about 5 carbon atoms in thehydroxyalkyl radical. Monoor diesters of the dicarboxylic acidsmentioned are included. Ordinarily, the acid and ester each comprisebetween about one percent and about 20 percent by weight of theinterpolymer, with the remainder being made up of one or more othercopolymerizable ethylenically unsaturated monomers. The most often usedare the alkyl acrylates, such as ethyl acrylate; the alkylmethacrylates, such as methyl methacrylate; and the vinyl 7 aromatichydrocarbons, such as styrene, but others can be utilized.

The above interpolymer is at least partially neutralized by reactionwith a base as described above; at least about 10 percent and preferably50 percent or more of the acidic groups are neutralized, and this can becarried out either before or after the incorporation of the interpolymerin the coating composition.

The amine-aldehyde condensation products included in these compositionsare, for example, condensation products of melamine, benzoguanamine, orurea with formaldehyde, although other amine-containing amines andamides, including triazines, diazines, triazoles, guanadines, guanaminesand alkyl and aryl-substituted derivatives of such compounds can beemployed, as can other aldehydes, such as acetaldehyde. The alkylolgroups of the products can be etherified by reaction with an alcohol,and the products utilized can be water-soluble or organicsolventsoluble.

Electrodeposition compositions comprising the above interpolymers and anamine-aldehyde resin are more fully described in U.S. Pat. No.3,403,088.

Still another electrodepositable composition of desirable propertiescomprises an alkyd-amine vehicle, that is, a vehicle containing an alkydresin and an amine-aldehyde resin. A number of these are known in theart and may be employed. Preferred are water-dispersible alkyds such asthose in which a conventional alkyd (such as a glyceryl phthalateresin), which may be modified with drying oil fatty acids, is made witha high acid number (e.g., 50 to 70) and solubilized with ammonia or anamine, or those in which a surface active agent, such as a polyalkyleneglycol (e.g., Carbowax), is incorporated. High acid number alkyds arealso made by employing a tricarboxylic acid, such as trimellitic acid oranhydride, along with a polyol in making the alkyd.

The above alkyds are combined with an amine-aldehyde resin, such asthose described hereinabove. Preferred are water-soluble condensationproducts of melamine or a similar triazine with formaldehyde withsubsequent reaction with an alkanol. An example of such a product ishexakis(methoxymethyl)melamine.

The alkyd-amine compositions are dispersed in water and they ordinarilycontain from about 10 percent to about 50 percent by weight of amineresin based on the total resinous components.

Yet another electrodepositable composition of desirable propertiescomprises mixed esters of a resinous polyol. These resin esters comprisemixed esters of an unsaturated fatty acid adduct. Generally the polyolswhich are utilized with these resins are essentially any polyol having amolecular weight between about 500 and 5000. Such resinous polyolsinclude those resinous materials containing oxirane rings which can beopened in, prior to, or during the esterification reaction to provide anapparent hydroxy site. The vehicle resins are formed by reacting aportion of the hydroxyl groups of the polyol with the fatty acid, theratio of the reactions being such that at least an average of onehydroxyl group per molecule of the polyol remains unreacted. Theremaining functionality is then reacted with the unsaturated fatty acidadduct of an olefinically unsaturated dicarboxylic anhydride, such asmaleic anhydride, this second esterification reaction being conductedunder conditions so that esterification occurs through the anhydridering, thereby introducing free acid groups into the molecule. Mixedacids of the class described are disclosed in Belgain Pat. No. 641,642,as well as in copending application Ser. No. 568,144, filed July 27,1966.

In order to produce an electrodepositable composition, it is necessaryto at least partially neutralize the acid groups present with a base inorder to disperse the resin in the electrodeposition bath. Inorganicbases such as metal hydroxides, especially potassium hydroxide, can beused. There may likewise be used ammonia or organic bases, especiallywater-soluble amines, such as, for example, the

mono-, diand tri-lower alkyl amines such as methylamine, ethylamine,propylene, butylamine, dimethylamine, diethylamine, dipropylamine,dibutylamine, rn-methylbutylamine, triethylamine, tributylamine,methyldiethylamine, dimethylbutylamine and the like; cyclic amines suchas morpholine, pyrrolidine, piperidine; diamines such as hydrazine,methylhydrazine, 2,3-t01uene diamine, ethyl diamine and piperizine andsubstituted amines such as hydroxylamine, ethanolamine, diethanolamine,butanolamine, hexanolamine and methyldiethanolamine, octanolamine,diglycolamine and other polyglycol amines, triethanolamine andmethylethanolamine, n-amino-ethanolamine and methyldiethanolamine andpolyamines such as diethylene triamine, triethylene tetramine,hexamethylene tetramine.

There may be present in the electrodepositable composition in additionto the oxides of manganese of the invention, any of the conventionaltypes of pigments employed in the art, for example, iron oxide, leadsilico chromate, strontium chromate, carbon black, titanium di oxide,talc, barium sulfate and the like, as well as combinations of these andsimilar pigments. Color pigments such as cadmium yellow, cadmium red,phthalocyanine blue, chrome yellow, toluidine red, hydrated iron oxide,and the like, may be included if desired. There is often incorporatedinto the pigment composition a dispersing or surface-active agent. Ifsuch a surface-active agent is used, it should be the non-ionic oranionic type in the case of polyacid vehicles or a combination of thesetypes. In the case of polybasic resins non-ionic or cationic agents arepreferred. Usually the pigment and surface-active agent, if any, areground together in a portion of the vehicle, or alone, to make a pasteand this is blended with the vehicle to produce a coating composition.

In many instances, it is preferred to add to the bath in order to aiddispersibility, viscosity and/or film quality, a non-ionic modifier orsolvent. Examples of such materials are aliphatic, naphthenic andaromatic hydrocarbons or mixtures of the same; monoand dialkyl ethers ofglycols, pine oil and other solvents compatible with the resin system.The presently preferred modifier is 4-methoxy-4- methylpentanone-Z(Pent.-Oxone).

There may also be included in the coating composition, if desired,additives such as antioxidants. For example, orthoamylphenol or cresol.It is especially advantageous to include such antioxidants in coatingcompositions which are used in baths which may be exposed to atmosphericoxygen at elevated temperatures and with agitation over extended periodsof time.

Other additives which may be included in coating compositions, ifdesired, include, for example, wetting agents such as petroleumsulfonates, sulfated fatty amines, or their amides, esters of sodiumisothionates, alkyl phenoxypolyethlene alkanols, or phosphate estersincluding ethoxylated alkylphenol phosphates. Other additives which maybe employed include anti-foaming agents, suspending agents,bactericides, and the like.

In formulating the coating composition, ordinary tap water may beemployed. However, such water may contain a relatively high level ofmetals and cations which, while not rendering the process inoperative,these cations may result in variations of properties of the baths whenused in electrodeposition. Thus, in common practice, deionized water,i.e., water from which free ions have been removed by the passagethrough ion exchange resins, is invariably used to make up coatingcompositions of the instant invention.

In addition to the electrodepositable vehicle resins described above,there may be present in the electrodepositable composition otherresinous materials which are noncarboxylic acid materials. For example,there may be added up to about 50 percent by weight of an amine-aldehydecondensation product. Examples of such aminealdehyde condensationproducts employed are aldehyde condensation products of melamine, urea,acetoguanamine or a similar compound and may be water-soluble or organicsolvent-soluble. Generally, the aldehyde employed is formaldehyde,although useful products can be made from other aldehydes such asacetaldehyde, crotonalde hyde, acrolein, benzaldehyde, furfural andothers. Condensation products of melamine or urea are the most commonand are preferred, but products of other amines and amides in which atleast one amido group is present can be employed.

For example, such condensation products can be produced with triazines,diazines, triazoles, quanadines, guanamines, and alkyl andaryl-substituted derivatives of such compounds, includingalkyl-substituted and aryl-substituted cyclic ureas, and alkylandaryl-substit-uted melamines. Examples of such compounds are:N,N-dimethyl urea, benzyl urea, N,N-ethylene urea, diazine diamide,formaguanamine, benzoguanamine, ammeline,2-chloro-4,6-diamino-1,3,5-triazine, 3,5-diaminotriazole,4,6-diaminopyrimidine, 2,4;6 triphenyltriamino-1,3,5-triazine, and thelike.

These aldehyde condensation products contain methylol groups or similaralkylol groups, depending upon the particular aldehyde employed. Ifdesired, these methylol groups can be etherified by reaction with analcohol. Various alcohols are employed for this purpose, includingessentially any monohydric alcohol, although the preferred alcohols aremethanol, butanol, and similar lower alikanols.

The amine-aldehyde condensation products are produced in a mannerwell-known in the art, using acidic or basic catalysts and varyingconditions of time and temperature. The aldehyde is often employed as asolution in water or alcohol, and the condensation, polymerization andetherification reactions may be carried out either sequentially orsimultaneously.

Other base-solubilized polyacids which may be employed aselectrodeposition vehicles include those taught in U.S. Pat. No.3,382,165, which is incorporated herein by reference, wherein the acidgroups rather than being solely polycarboxylic acid groups containmineral acid groups such as phosphonic, sulfonic, sulfate, and phosphategroups.

The process of the instant invention is equally applicable to cationictype vehicle resins, that is, polybases solubilized by means of an acid,for example, an amineterminated polyamide or an acrylic polymersolubilized with acetic acid. One such class of materials is describedin British Pat. 1,132,267. Another case of such cationic polymers isdescribed in copending application Ser. No. 772,366, filed Oct. 28,1968.

In a manner similar to the anionic resins described above, the cationicresins may be formulated with adjuvants, such as pigments, solvents,surfactants, crosslinking resins, and the like.

The polyacids are anionic in nature and are dispersed or dissolved inwater with alkaline materials such as amines or alkaline metalhydroxides and, when subjected to an electric current, they migrate tothe anode. The polybasic resins, solubilized by acids, are cationic incharacter and when these resins are water dispersed or solubilized withan acid such as acetic acid, the material deposits on the cathode underan electric current.

The oxides of manganese are introduced into the compositions of theinvention in the same manner as conventional pigments are dispersed.Preferably, the oxides of manganese are reduced to a small particlesize, usually less than about 25 microns and, more preferably, belowabout 10 microns before being added to the vehicle. If large particlesof oxide are introduced, the grinding will require more time and perhapsa filtration step to remove oversized particles remaining.

The oxides are dispersed by grinding, usually in the presence of atleast a portion of the vehicle resin and, in most cases, a surfactant ordispersing agent. Grinding is accomplished by the use of ball mills,sand mills,

10 Cowles dissolvers, continuous attritors, until the pigmelll. has beenreduced to the desired size and, preferably, has been wet by anddispersed in the vehicle resin and/or dispersing agent.

In the case of polyacid vehicle resins, preferably the grinding isconducted in an aqueous dispersion of neutralized resin having a pHabove about 7 and preferably about 9.0. The amount of water present insuch an aqueous grind is not critical; however, commonly the resinemployed in the grinding step is about 30 to 70 percent solids. The useof more water merely reduces the effective capacity of the mill andwhile less water can be employed, the viscosity creates some problems incertain instances.

The pigment-binder ratio in the grinding step is not critical; however,levels between about 3.5/1 and 7/1 are frequently employed, althoughother levels may be utilized.

After grinding the particle size should be in the range of 10 microns orless, preferably as small as practicable. Generally a Hegman Grind gaugereading of about 6 is the minimum for a presently commerciallyacceptable composition.

For a general review of pigment grinding and paint formulation,reference may be had to: D. H. Parker, Principles of Surface CoatingTechnology, Interscience Publishers, New York 1965); R. L. Yates,Electropainting, Robert Draper, Ltd., Teddington, England 1966); H. F.Payne, Organic Coating Technology, vol. II, Wiley & Sons, New York1961).

It has been found especially important to regulate the ratio of pigmentto the vehicle in compositions which are used in electrodepositableprocesses. In most instances the most desirable coatings are obtainedwhen the coating composition contains a ratio of pigment-to-vehicleratio of not lower than 0.8 to 1 and preferably not higher than 2 to 1.If the composition has too high a pigment-toyehicle ratio, theelectrodeposited films may exhibit very poor flow characteristics and,in many instances, are noncontinuous and have poor film appearance.

In the electrodeposition process, a process well-described in the art,the aqueous bath containing the composition is placed in contact with anelectrically conductive anode, and an electrically conductive cathode.The coating is deposited upon the appropriate electrode so that theconductive substrate to be coated is used as that electrode. Uponpassage of electric current normally direct current) between the anodeand the cathode, while in contact with the bath containing the coatingcomposition, an adherent film of the coating composition is deposited onthe appropriate electrode.

The conditions at which the electrodeposition process is carried out arethose conventionally used in electrodeposition. The applied voltage mayvary greatly and can be as low as, for example, one volt, or as high,for example, as 500 volts or higher. It is typically between 50 and 350volts. The current tends to decrease during electrodeposition and thefilms become electrically insulative and cause the deposition of film tobe self-terminating at any particular voltage.

The electrode coated may be any electrically conduc tive metal, such asiron, steel, aluminum, galvanized steel, phosphatizled steel, zinc, andthe like.

The concentrations of the coating composition in the aqueous bath usedin electrodeposition is not critical and relatively high levels ofcoating composition can be used. However, it is ordinarily desirable touse a low concentration of coating composition since this is one of thebenefits inherent in the system. Baths containing as little as onepercent by weight of the coating composition in water can be employed.In general practice, the baths used usually contain between 5 and about15 percent by weight of paint solids. Generally it is preferred not touse more than 20 or 25 percent by weight of the coating composition inthe bath, although there is no technical reason why films cannot beproduced in even higher levels. Once the film is deposited upon thesubstrate and the substrate removed from the bath, the article istreated as one which has been coated in the conventional paintingoperation. The article may be air-dried, or, usually, it is heated in anoven or by some other appropriate means to bake or dry the film. Whenthis is done, the baking temperatures of about 275 F. to about 375 F.for 60 to 10 minutes are usually employed.

Throw power, the ability of an electrodeposition material to coat thinareas remote or shielded from the cathode, is measured by taking a stripof mil phosphatized steel stock, 14.5 inches long by 0.5 inch wide, andpunching the center of a 0.31 diameter hole 0.75 inch from one end ofthe strip and centering it in a 14 inch section of standard gas conduit(0.75 inch standard diameter), the upper 0.5 inch of which is partiallycut off to allow bolting to an electrode support by means of a 0.31 inchdiameter hole, the center of which is 0.5 inch distance from the upperend of the tube. The strip is inserted into the tube and both arefastened to electrode holders with a wing nut. The lower end of thestrip is flush with the end of the tube. The strip-tube electrodeassembly is connected to the positive terminal and the metal coatingtank to the negative terminal. The height of the coating tank shouldpermit immersion of the electrodes to a depth of inches. The exactclearances between the electrode assembly and the bottom and sides ofthe tank are not critical. In the tests conducted in the examples, thetank was a circular stainless steel tank with an internal diameter ofapproximately 5 inches and the bottom of the pipe was at least an inchabove the bottom of the tank. Unless otherwise stated, theelectrodeposition conditions were those which give 0.8 mil filmthickness on a panel in two minutes. A power test was likewise conductedfor two minutes unless otherwise specified. After coating, this strip isrinsed and baked at the schedule prescribed for the coating and thenslightly rubbed with a soft pencil eraser at the feathered edge of thebaked coating of the strip. The length of the coating remaining on thestrip is measured and recorded as the relative throw power.

Acid values are conducted in the instant specification and wereconducted in accordance with ASTM standard method 5554 and equivalent.An acid value may be defined as the milligrams of KOH necessary toneutralize a one-gram sample of the resin composition being tested. Thismethod titrates only one half of the anhydride carboxyls.

The salt spray tests utilized in the examples are essentially equivalentto ASTM Test D11762 and involve exposing a scribed panel to a fog of asalt solution comprising 5 parts by weight salt and 95 parts distilledwater at a relative humidity of 100 and a temperature of 95 F.

The saponification test conducted in the examples involves placing thepanel to be tested in a normal sodium hydroxide solution at 100 F.

The invention is further described in conjunction with the followingexamples, which are to be considered illustrative rather than limiting.All parts and percentages in the examples and throughout thisspecification are by weight unless otherwise stated.

EXAMPLE A A vehicle composition was produced by heating a 4-to-1 weightmixture of linseed oil and maleic anhydride under an inert gas blanketat 510 F. for 5 hours to obtain a resin having a final acid value ofabout 80 and a Brookfield viscosity of 90,000 centipoises.

EXAMPLE B A maleinized tall oil fatty acid adduct was prepared bycharging into a reaction vessel fitted with agitator, thermometer, inertgas inlet and reflux condenser, 784 parts of maleic anhydride and 2280parts of tall oil fatty acids. The air in the reactor was displaced withan inert 12 gas blanket and the contents heated to C. to melt the maleicanhydride. The reaction mixture was then agitated and heated slowly toabout 225 C. in about two hours, then to 260 C. in an additional hour.The reaction was held at 260 C. for an additional three hours. Thereaction product had a viscosity of 5,000 centi oises, and an acid valuedetermined in alcoholic KOH of 255.

EXAMPLE C Into a reactor equipped with an agitator, thermometer, inertgas tube, reflux condenser and water trap were added 1600 parts of astyrene-allyl alcohol copolymer having the repeating structure:

having a molecular weight of approximately 1600, equivalent weight inthe range of 285 to 315; 1070 parts of tall oil fatty acid and 60 partsof xylene. The reaction mixture was heated with agitation and slow inertgas sparge to 250 C. and held until an acid value of approximately 5 wasreached, which was approximately 4 /2 hours after reaching 250 C. Thewater of esterification was removed by the water trap. The reactionmixture was then vigorously sparged with inert gas to remove the xyleneand cooled to C. There was then added, with stirring, 480 parts of theresin produced in Example B. The reaction mixture was heated to 145 C.and held at that temperature for 45 minutes. The reaction mixture wasthen cooled below C. and there was added with stirring 341 parts ofPent-Oxone. This resin mixture had a final acid value of 36 and aBrookfield viscosity of 52,- 000 centipoises.

EXAMPLE D Into a reactor equipped with a thermometer, inert gas inlet,water trap, condenser and agitator was added 217.5 parts of ahydrocarbon resin Piccodiene 9215, an unsaponifiable, unsaturated resinpossessing an iodine value of about 180, a softening point of about 100C., and a molecular weight between about 250 and 900, derived from thepolymerization of cyclic, straight and branch chain olefins obtainedfrom petroleum cracking and 345 parts of dehydrated castor oil. Theabove mixture was agitated under inert gas sparge and heated to 250 C.and held for about one hour to a Gardner-Holdt viscosity of TU. Themixture was then cooled to 100 C., the inert gas sparge beingmaintained. There was then added 75 parts of maleic anhydride and themixture heated to 225 C. without inert gas sparge. The temperature washeld for about one hour to a Gardner-Holdt viscosity of V-W. Thereaction mixture was then blanketed with inert gas and there was added112.5 parts of raw castor oil. After 15 minutes of cooling, at atemperature of C., there was added 80 parts of Pent-Oxone. The resin hada final acid value of 53 and a Brookfield viscosity of 85,000centipoises.

EXAMPLE I Parts by wt. Maleinized linseed oil adduct (Example A) 51.2Diethylamine 5. l

The above mixture was stirred 45 minutes under cover and then there wasadded at room temperature:

Cresylic acid Deionizcd water After thorough mixing there was added:Parts by wt.

Deionized water 32.0 Dispersing agent (combination oil-soluble sulfonatenon-ionic surfactantWitco 912) 3.5

After further mixing there was added:

Diethylamine 7.0 Deionized water 40.0

The pH was adjusted to 11.0 with diethylamine and there was added:

Manganese dioxide (MnO (325 mesh) 132.4 Strontium chromate 7.0

The mixing was continued and the pH was adjusted with diethylamine to9.6. The above mixture was ground for five minutes in a steel ball milland the pH adjusted to 9.1. The grinding was continued for 25 minutes toobtain a No. 7 Hegman grind gauge reading. There was then added 35 partsdeionized water as a mill wash and the grinding was continued foradditional minutes. This was designated Paste I.

A solubilized vehicle (resin I) was prepared as follows:

Premix I: Parts by wt. Diethylamine 55.6 Deionized water 1392.0

Premix II:

Vehicle resin of Example D 1284.0 Pent-Oxone 170.0 Cresylic acid 12.8

Premix H was added slowly to premix I with stirring. There was thenadded:

Deionized water 404.0

The electrodeposition composition was prepared as follows:

To solubilized vehicle resin I 806.9

there was added slowly, with stirring:

Paste I 160.8

After thorough mixing, there was added:

Deionized water 2732.3

EXAMPLE II A composition was prepared as follows: A pigment paste (pasteII) was made by shaking the following mixture in a steel canistercontaining steel balls.

Parts by wt. Tall oil fatty acid ester (as Example B) 69.5 Pent-Oxone(4-methoxy-4-methyl-pentanone-2) 8.0 Cresylic acid 0.6

The above was mixed thoroughl yand then there was added:

Triethylamine 4.7

Mixing was continued and there was added:

Deionized water 73.4

14 The mixture was adjusted to a pH of 9.25 with triethylamine. Thenthere was added with continuous mixing:

Parts by Wt. Dispersing agent (combination oil-soluble sulfonatenon-ionic surfactant-Witco 912) 2.5 Deionized water 30.0 Triethylamine3.0

Under continuous agitation the pH was adjusted to 10.25 withtriethylamine. Then there was added:

Manganese sesquioxide (325 mesh) 187.5 China clay 50.0 Strontiumchromate 12.5

The milling was commenced and after 5 minutes the pH was adjusted withtriethylamine to 9.8. There was then added:

Deionized water Triethylamine The shaking was continued an additional 30minutes to obtain a maximum grind of 6% to 7 Hegman reading. There wasadded with continued shaking:

Deionized water 40.0

This was designated paste II.

The electrodeposition primer was formulated as follows:

A solubilized vehicle resin was prepared as follows:

Parts by wt.

Mixed ester vehicle resintall oil fatty ester (as in Example C) 304.6Pent-Oxone (4-methoxy-4-methy1-pentanone-2) 35.3 Cresylic acid 2.7

The above was mixed thoroughly and then there was added:

Triethylamine 20.6

Mixing was continued and there was added:

Deionized water 322.1

and the pH of the mixture was adjusted to 9.25 with triethylamine.

To this solubilized vehicle resin was then added 179.8 parts by weightof pigment paste (Paste II), supra, and mixed thoroughly. Then there wasadded with continuous mixing:

Deionized water 2984.9

The pH was adjusted to 9.2 with triethylamine.

The above composition was deposited on polished phosphatized steelpanels at a bath temperature of 76 F., at a voltage of 310 volts for twominutes. A film thickness of 0.7 mil was obtained. The panel was bakedfor 25 minutes at 360 F. After 250 hours salt spray exposure, about 1mm. scribe liftage was observed, as well as some pinpoint blisters. Thebath displayed a throw power of 5% inches at two minutes.

EXAMPLE A composition was prepared as follows: A pigment paste (pasteIII) was made by shaking the following mixture in a steel canistercontaining steel balls.

Premix I: Parts by wt. Diethylamine 4.4 Deionized water 95.6

Premix II:

Hydrocarbon-castor oil-maleic resin (as in Example C) 99.2 Cresylic acid0.8

Premix II was slowly added to premix I under continuous agitation andthe resulting mixture was agitated for an additional 10 minutes. Thenthere was added:

Dispersing agent (combination oil-soluble sulfonate non-ionicsurfactantWitco 912 3.6 Deionized water 50.0 Diethylamine 2.0

The above was thoroughly mixed for 10 minutes and then there was added:

Parts by wt. Manganese sesquioxide (325 mesh) 148.8 China clay 79.2Strontium chromate 12.0

The pH was adjusted to 9.3 with diethylamine and then there was addedunder continuous mixing:

Diethylamine Deionized water Deionized water 25.0

The electrodeposition primer was formulated as follows:

Two premixes were prepared as follows.

Premix I:

Diethylamine 16.5 Deionized water 358.0 Premix II:

Hydrocarbon-castor oil-maleic resin (see Example C) 371.5 Cresylic acid3.0

Premix II was slowly added to Premix I under continuous agitation. Theresulting combined mixture of premix I and premix II was agitated for anadditional 10 minutes.

Then there was slowly added with continuous agitation 153.1 parts byweight of pigment paste (paste. III, supra) to the above premix mixture.There was added:

Parts by wt. Deionized water 2948.7

The pH was adjusted to 9.1 with diethylamine.

The above composition was deposited on polished phosphatized steelpanels at a bath temperature of 78 F., at a voltage of 350 volts for 2minutes. A film thickness of 0.85 mil was obtained. The panels werebaked at 360 F. for minutes. The films had an excellent appearance.After 250 hours salt spray exposure, a 3 mm. scribe liftage wasobserved.

The bath had a throw power of 5% inches at two minutes.

One outstanding feature of this invention is that in the case of vehicleresins which contain drying oil, the oxides of manganese function as adrier as well as an excellent pigment. Difiiculty, such as stability,has been encountered when conventional driers such as naphthanates andoctoates have been added to an electrodeposition bath. The oxides ofmanganese promote drying of such vehicle resins without markedlyincreasing bath instability. This drying effect is demonstrated asfollows:

EXAMPLE An electrodepositable composition was prepared as follows:

Pigment pastes (paste IV and paste V) were prepared by grinding thefollowing mixtures in a steel ball mill:

Parts by wt. Maleinized linseed oil adduct (as in Example A) 51.0Diethylamine 8.0 Deionized water 189.0

After thorough mixing of the above, there was added (in the case ofpaste IV):

Cresylic acid 6.0 Dispersing agent (combination oil-soluble sulfonatenon-ionic surfactantWitco 912) 19.0

Manganese dioxide (325 mesh) 211.0 Strontium chromate 24.0

and, in the case of paste V, carbon black replaced the manganese dioxidein the above composition.

Electrodepositable compositions were formulated as follows:

Parts by wt. Vehicle resin of Example A 294.0 Diethylamine 27.9

The above was mixed under cover for 45 minutes at room temperature andthere was then added:

Cresylic acid 2.9

After mixing the above, the mixture was then thinned to one gallon,adding in one instance (bath IV) grams of paste IV, and in a secondinstance, 84 grams of paste V.

Phosphatized steel panels were electrocoated with 0.7 mil of each of theabove. The panels were then baked 30 minutes at 250 F. The manganeseoxide-containing coating was substantially tack free, while the coatingcontaining carbon black remained tacky.

Various other electrodepositable compositions, such as those hereinabovedescribed, can be substituted for those of the examples. In the aboveand other tests, the general applicability of the composition andmethods herein have been shown and it has been found that good resultsare attained using varying compositions, electrodeposition conditionsand substrates.

According to the provisions of the patent statutes, there are describedabove the invention and what are now considered its best embodiments;however, within the scope of the appended claims, it is to be understoodthat the invention can be practiced otherwise than is specificallydescribed.

What is claimed is:

1. In an aqueous electrodepositable composition comprising an ionicallysolubilized synthetic organic vehicle resin and a black pigment, theimprovement comprising employing as a black pigment, in pigmentary formand amount, an oxide of manganese selected from the group consisting ofMn O Mn O MnO and naturally-0ccurring mineral oxides containing thesame.

2. A composition as in claim 1 wherein the pigmentbinder weight ratio isbelow about 1 :1.

3. A composition as in claim 1 wherein the oxide of manganese isselected from the group consisting of manganese dioxide and manganesesesquioxide.

4. A composition as in claim 3 wherein the pigmentbinder weight ratio isbelow about 1: 1.

5. A composition as in claim 1 wherein the vehicle resin comprises abase-solubilized synthetic polycarboxylic acid vehicle resin.

6. .A composition as in claim 5 wherein the pigmentbinder weight ratiois below about 1:1.

7. A composition as in claim 5 wherein the oxide of manganese isselected from the group consisting of manganese dioxide and manganesesesquioxide.

8. A composition as in claim 7 wherein the pigmentbinder weight ratio isbelow about 1:1.

9. A composition as in claim 5 wherein the vehicle resin comprises abase-solubilized driable polycarboxylic acid resin.

10. A composition as in claim 9 wherein the pigmentbinder weight ratiois below about 1: 1.

11. A composition as in claim 9 wherein the oxide of manganese isselected from the group consisting of manganese dioxide and manganesesesquioxide.

12. -A composition as in claim 11 wherein the pigmentbinder weight ratiois below about 1: l.

13. A composition as in claim 12 wherein the vehicle resin comprises amaleinized drying oil fatty acid ester.

References Cited UNITED STATES PATENTS 7/1968 Vertnik 26029.6X 11/1968Hwa 26029.6

OTHER REFERENCES Chemistry of Paints, Pigments, and Varnishes; Bearn;Van Nostrand; NY. 1924; pages 2423.

10 DONALD E. CZAJ A, Primary Examiner C. W. IVY, Assistant Examiner

